Severe headache at the right side of the back of the head. onset with alcoholic drinks. lasting for 2wks. clear mri. cluster hdache or occptl neurgla?

Muscle spasm: Perhaps with alcohol you slept with head in strange position causing muscle spasm and pain where the superior trapezius and levator scapula muscles insert on the back of the skull. Massage and heating pad might ameliorate. A local cortisone injection into the muscle tendon could dramatically dissipate if it is tendonitis. Likely "occipital neuritis" due to muscle spasm.

Hard to tell: Migraines are usually one-sided, pounding, severe headaches that last up to 3 days and have associated nausea, incapacity, and vision change. Alcohol can be a trigger. I'm glad your MRI is clear, because that rules out tumor. These could be either cluster or occipital neuralgia. The next step might be to get an injection to block that right occipital nerve and possible physical therapy.